(1) Field of the Invention
The present invention relates to a near infrared ray-decolorizable recording material capable of being decolorized with a near infrared ray, and a toner and ink containing the near infrared ray-decolorizable recording material as a colorant.
(2) Description of the Related Art
Conventionally, in the fields of, for example, printing and copying, the storability of a recording material, in terms of environmental resistance, e.g., light resistance, moisture resistance, resistance to solvent, and thermal resistance, has become increasingly important, and thus many attempts have been made to improve the physical properties of dyes and pigments. Particularly, many developments have been made in the fields of electrophotographic recording, electrostatic recording, and thermal transfer-ink recording. Recently, due to the increasing amount of information available, a repeated printing has been required, and photochromic materials and thermalchromic materials have been developed as recording materials for multiple recording systems or rewritable recording materials (see, for example, Japanese Unexamined Patent Publication (Kokai) No. 60-155179, Japanese Unexamined Patent Publication (Kokai) No. 50-75991, and Japanese Unexamined Patent Publication (Kokai) No. 50-105555.
Japanese Unexamined Patent Publication (Kokai) No. 60-155179 discloses flugide compounds which appear blue under ultraviolet rays and are transparent under a white light, and Japanese Unexamined Patent Publication (Kokai) No. 50-75991 discloses a thermally discoloring material comprising a coupler consisting mainly of a leuco-dye, and a phenolic hydroxy group-containing compound as a developer. These rewritable recording materials, however, are reversibly decolored and colored or subjected to color changes by a visible light or ultraviolet rays, and further, have problems in terms of storage stability under visible light and durability to repeated recording.
Further, many similar studies have been made in the fields of electrophotographic recording and electrostatic recording, as well as in the fields of printing inks and inks for printers, and many electrophotographic printing methods are known, for example, as disclosed in U.S. Pat. No. 2297691, Japanese Examined Patent Publication (Kokoku) No. 42-23910, and Japanese Examined Patent Publication (Kokoku) No. 43-24748. In general, an electric latent image is formed on a sensitizing material, utilizing a photoconductive substance in many ways, the latent image is developed with a toner to form a visible image, and optionally, after the toner image is transferred to a material such as paper, the image is fixed by the application of heat and pressure to obtain a copy. Furthermore, various developing processes wherein an electrostatic image is obtained by using a toner are known. For example, various developing processes, such as the magnetic brush process disclosed in U.S. Pat. No. 2874063, the cascade developing process disclosed in U.S. Pat. No. 2,618,552, the powder-cloud process disclosed in U.S. Pat. No. 2,221,776, the fur brush developing process, and the liquid developing process, etc. are known. Various magnetically recording processes wherein a magnetic latent image is formed and then developed with a magnetic toner are also known. The toner image when developed is optionally transferred to a material such as paper, and then fixed. As processes for developing the toner image, a process wherein the toner is heated and melted by a heater or heated roller, to be fused to a base material and followed by solidification, a process wherein the binder resin of the toner is softened or dissolved with an organic solvent to be fixed on a base material, and a process wherein the toner is fixed on a base material by the application of pressure are known.
The toners used in the fixing process using heating rollers as described above are generally prepared by melt mixing and uniformly dispersing a colorant such as carbon black, and additives such as an electric charge regulator, in a thermoplastic resin such as a styrene-butyl acrylate copolymer, allowing the mixture to cool, and then finely pulverizing the solidified product into a desired particle diameter by a pulverizer or dispersing machine. Furthermore, currently a coloration is under development in the printing and copying fields, and an improvement of the physical properties of colorants and electric charge regulator is widely sought (see, for example, Japanese Unexamined patent publication (Kokai) No. 57-130046 and Japanese Unexamined patent publication (Kokai) No. 57-191650).
Many printing processes, such as off-set press printing, letterpress printing, gravure printing, transfer press printing, or specific press printing inclusive of flexographic printing, metal printing, plastic printing, and glass printing, as well as electric printing by printers such as impact printers or non-impact printers in the printing field are known, and the inks used consist mainly of a vehicle, a binder, and a colorant such as a dye or pigment. Further, recently, the development of ultraviolet curing inks for preventing pollution by not using solvents, improving productivity by a rapid curing, or improving the physical properties of the cured coat have been proposed (see, for example, Japanese Unexamined patent publication No. 1-229084, Japanese Unexamined patent publication (Kokai) No. 1-271469, and Japanese Unexamined patent publication (Kokai) No. 2-22370).
Nevertheless, thermal color-changing materials such as the photochromic material and leuco-dye as described above have a poor image stability under visible light. Furthermore, the above-mentioned toners for electrophotographic recording and printing inks have problems in that, after being set, the set image cannot be decolorized, the recording portion cannot be set again, and the recording paper can not be reused, and further, a problem arises in terms of keeping the accompanying disposal treatment content of disposed papers secret.